1. Field of the Invention
The present invention relates to a seatbelt device for securing an occupant to a seat with a seatbelt and ensuring the safety of such occupant upon a vehicle collision.
2. Related Art
A known seatbelt device comprises a collision detector for detecting a vehicle collision and outputting a collision signal, an airbag deploying in response to the collision signal, and a seatbelt device having a pretensioner for retracting a seatbelt in response to the collision signal.
However, according to this invention, a large amount of the seatbelt is protracted if, for example, an occupant is wearing clothes made of a thick material. Consequently, the amount of the seatbelt that needs to be wound would be large, because in order to effectively secure an occupant with a seatbelt device having a pretensioner, the seatbelt must have a tension above a prescribed value. If it takes time to effectively secure the occupant after an order for activating the pretensioner is given, the occupant is in the meantime displaced forward in the direction of the collision, entering the zone where the airbag is deploying. In other words, an occupant entering the airbag deployment zone while the airbag is deploying may contact the airbag and hit his/her head against the inflating airbag at the speed of its deployment. Furthermore, winding of the seatbelt is delayed if the detection of the vehicle collision is delayed, whereby the occupant is displaced in the direction of the collision. Here also, the occupant may be displaced to the airbag deployment zone and hit his/her head against the airbag.
Furthermore, for the safety of the occupants it is preferred that any vehicle employing a seatbelt device simply in combination with an airbag has its seatbelt device exchanged to a seatbelt device comprising a pretensioner. In such case, a traditional collision detector must also be exchanged to a collsion detector capable of driving both an airbag device and a pretensioner, but this increases the number of parts which needs to be exchanged and is also costly.